fázisátmeneteknek

Fázisátmenetek, in English phase transitions, refer to the physical processes that occur when a thermodynamic system changes from one state (phase) to another. These transitions are typically driven by changes in external conditions such as temperature, pressure, or magnetic field. Common examples include the melting of ice into water, the boiling of water into steam, and the condensation of steam back into water.

Phase transitions can be classified based on the behavior of thermodynamic potentials and their derivatives. First-order phase transitions involve a discontinuity in the first derivative of the thermodynamic potential, such as enthalpy or volume. During these transitions, latent heat is absorbed or released, and there is a coexistence of phases at the transition point. Examples include melting, boiling, and sublimation.

Second-order phase transitions, also known as continuous phase transitions, are characterized by a discontinuity in the second derivative of the thermodynamic potential, such as specific heat or compressibility. These transitions do not involve latent heat, and the change in properties occurs gradually rather than abruptly. Examples include the ferromagnetic to paramagnetic transition in materials and the transition to superconductivity.

The study of phase transitions is a fundamental area in condensed matter physics and statistical mechanics. It helps understand the collective behavior of matter and the emergence of macroscopic properties from microscopic interactions. Concepts like critical phenomena, universality, and symmetry breaking are crucial in describing these transitions, especially near their critical points where fluctuations become significant and long-range correlations develop.